Patent GB-722156-A (GB)
Title: Improvements in or relating to the protection of electrically propelled vehicles
IPC: B60L3/06
Filed: 1952-09-03
Abstract: 722,156. Protective cut-out arrangements. control of D.C. motors. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Sept. 3, 1952 [Sept. 11, 1951], No. 22169/52. Classes 38 (3) and 38 (5) In an electrically-propelled vehicle having a relay PR responsive to earth fault currents in an earth connection 979, 44 to the secondary circuit of a transformer 17, 19 and a vehicle-carried source of auxiliary power for retraction of a pantograph 15 or other current-collecting means and for other purposes, a control means causes the initial completion of the earth connection only at a time when the source of auxiliary power is in a satisfactory operating condition. In the arrangement shown, the control means is a pneumaticallyoperated relay H which is controlled by a normally open, electromagnetic valve V3 and a pressure-responsive valve V4. When the air pressure is sufficient, the valve V4 opens and the relay H is operated to close its contacts 82, 86, 51 and 88. The closing of contacts 86 completes a circuit for a delay GAC which at contacts 42 completes the earth connection 979, 44 and at contacts 87 closes a holding circuit. The relay PR includes a shaded pole induction motor 54 with operating coils 55, 56 responsive to overload currents in the transformer primary circuit 17, and coils 57 energized by the difference current in current transformers 60, 61 to give protection against internal earth faults on the transformer primary winding. The coils 57. may also be energized from a current transformer 58 by earth fault currents flowing in the earth connection 979, 44 in the event of an earth fault in any of the transformer secondary circuits. When the relay PR is energized it initially'opens contacts A to cause the opening of the relay H to effect the de-energization of the various transformer secondary circuits. If the fault persists, contacts B are then closed to energize the coil of an electromagnetic valve GS which opens to cause the closing of a pneumatically-operated switch 33. This switch completes a short-circuiting connection and the resulting heavy currents cause the opening of a substation circuit breaker 14. The relay PR now being de-energized, its movable element can return to position where contacts C are closed to effect the opening of a valve V2 and the retraction of the pantograph 15. In the arrangement shown, the motor is supplied with direct current from ignitrons 1A, 1B and the voltage applied to the motor is controlled by tapchanging contactors C1 ... C12 which are controlled by a motor controller MC. When the controller is moved into " run " position a relay FC is energized to remove at 91, a short-circuit from the firing-circuit of the ignitrons and at contact 92 to cause the energizing of line switches L1, L2 which close the ignitron anode circuits. Switch L2 at contacts 97 causes the de-energizing of relay GAC which opens contacts 42 to disconnect the earth connection 979, 44 and at contacts 52 completes an earth connection 992-53 which includes the operating coil GDC of an earth fault relay having contacts 89 to effect the opening of the line switches L1, L2 and relay FC should an earth fault occur in the secondary circuits when the motor is in use. Specification 682,610 is referred to.